This invention relates generally to imaging methods and apparatus, and more particularly, to methods and apparatus that provide for improvements in x-ray detector fabrication.
X-ray detectors typically include a photodiode portion and a scintillator portion. An x-ray enters the detector and impinges the scintillator material, wherein photons of visible light are created. The visible light then leaves the scintillator material and impinges a photodiode. The photodiodes are polled, returning attenuation measurements. This data is then used to create images.
Currently most of the scintillator ceramics are made from wet chemical processes. The wet chemical processes include dissolving all the ingredients in acid to make a homogeneous solution and the coprecipitation to convert the solution into a slurry. For instance, some scintillator ceramics are made with the oxalate coprecipitation processes. First Y2O3, Gd2O3, Eu2O3, and other dopants are dissolved in nitric acid to prepare a nitrate solution. The nitrate solution is mixed with an oxalic acid solution through dual flow and mixing. During the mixing, the nitrate reacts with the oxalic acid to form insoluble oxalate (a mixture of yttrium oxalate, gadolinium oxalate, europium oxalate, and the oxalate of other dopants). Then the oxalate is filtered and washed with DI water (deionized). The wet cake is dried after filtration. The dried powder is then milled and calcined to form an oxide powder. The oxide powder is dry compacted and sintered into a transparent ceramic. The process for Lu—Tb—Al—O based garnet scintillator is very similar. A sulfate or nitrate solution is first prepared, then the solution is mixed with ammonium hydroxide solution to form the Lu—Tb—Al hydroxide gel as a slurry. The slurry is filtered, washed, dried, milled, and calcined sequentially afterwards.
One problem of this process is the agglomeration of powder and the complexity of the processes. Therefore, it is desirable to have a nanometer sized powder process for the ceramic scintillators to achieve a relatively high transparent scintillator material with a relatively lower sintering temperature and to reduce defects and manufacturing cost.